Atrasentan is a potent and selective antagonist for the endothelin A (ETA) receptor. It previously was evaluated in clinical trials for the treatment of prostate cancer at daily doses ranging from 2.5 mg to at least 95 mg. Lower daily doses of atrasentan currently are being evaluated in clinical trials for the treatment of chronic kidney disease associated with Type II diabetes. Although the proprietary atrasentan pharmaceutical dosage forms most recently employed in these clinical trials were suitable for such clinical trials, they did not exhibit the longer-term stability profile needed for a commercial drug product. Accordingly, there is a need for atrasentan pharmaceutical dosage forms having improved stability profiles that comply with regulatory requirements and are suitable for commercial use.